Lignocellulosic biomass (LCB) could serve as a primary carbohydrate feedstock to partially replace petroleum-based fuels and chemicals. LCB of terrestrial plants is composed of the thermoplastic lignin (15-25%) and two carbohydrate polymers, cellulose (35-50%) and hemicellulose (20-35%). Processes for depolymerization and fermentation of LCB are more complex and more capital intensive than established technologies for cornstarch or cane syrup. Unlike the starch, LCB has been designed by nature to serve as a structural element that resists microbial deconstruction. Pretreatments such as dilute mineral acids or base treatments are needed to render cellulose polymers accessible to enzymatic attack. Steam treatment with dilute mineral acids hydrolyzes hemicellulose into a pentose-rich syrup. This process is accompanied by side reactions and the production of inhibitors (furans, organic acids, and phenolics) that retard fermentation.